Collaborative Measurements in Cellular Networks

1. A method for assessing interference in a wireless network, comprising: causing an interfering transmitter in the network to transmit data in accordance with at least one predefined time-frequency-pattern, which specifies a first set of time-frequency resources at fixed first positions relative to a start of a specified frame, in which the interfering transmitter is to transmit first interfering signals at a first interfering power level and a second set of time-frequency resources at fixed second positions relative to the start of the specified frame, in which the interfering transmitter is to transmit second interfering signals at a second interfering power level, lower from the first interfering power level, while a serving transmitter transmits downlink signals to user equipment; instructing the user equipment to measure and report at least one parameter associated with reception of the downlink signals that is indicative of an effect of the interfering signals on the reception while the interfering transmitter operates in accordance with the predefined time-frequency pattern; and receiving and processing measurement results reported by the user equipment in order to assess the effect of the interfering signals.

2. The method according to claim 1 , wherein the method comprises optimizing transmission of the downlink signals responsively to the effect of the interfering signals.

3. The method according to claim 1 , wherein the serving transmitter belongs to a serving base station in the network.

4. The method according to claim 3 , wherein the interfering transmitter belongs to one of a plurality of interfering base stations in the network.

5. The method according to claim 3 , wherein the serving base stations and the interfering base stations operate in accordance with a standard of the Third-Generation Project Partnership (3GPP).

6. The method according to claim 5 , wherein the predefined time-frequency pattern extends over multiple transmission frames, each frame containing multiple subframes at respective positions within the frame.

7. The method according to claim 6 , wherein the multiple transmission frames comprise at least first and second frames, and wherein the subframes that are allocated to the first and second sets alternate between the first and second frames.

8. The method according to claim 1 , wherein the serving transmitter transmits the downlink signals at a constant power level within both the first and the second set of time-frequency resources.

9. The method according to claim 1 , wherein the interfering transmitter transmits the downlink signals at a constant downlink power level within both the first and the second set of time-frequency resources.

10. The method according to claim 1 , wherein processing the measurement results comprises comparing the at least one parameter reported by the user equipment with respect to the first set of the time-frequency resources to the at least one parameter reported by the user equipment with respect to the second set of the time-frequency resources.

11. The method according to claim 1 , wherein the first and second sets of time-frequency resources have fixed, respective first and second positions relative to a start of frame over multiple transmission frames.

12. The method according to claim 1 , where the second interfering signals comprise only Almost Blank Subframes or zero-power transmission.

13. The method according to claim 3 , where the serving base station is requested by a management entity to transmit the downlink signals over a specified set of time-frequency resources at specific power levels during a measurement interval.

14. The method according to claim 4 , where causing the interfering transmitter to transmit comprises sending a message from the serving base station to one of the interfering base stations to transmit the data in accordance with the at least one predefined time-frequency pattern.

15. The method according to claim 1 , where the time-frequency pattern is allocated over a full frequency channel or over one or more physical resource blocks.

16. The method according to claim 1 , where the time-frequency pattern takes into account a lack of perfect synchronization between the serving transmitter and the interfering transmitter.

17. A wireless base station, comprising: a radio interface, configured for communicating over a wireless network with user equipment; a communication interface, configured for exchange of messages with other base stations in the wireless network; and a processor, which is configured to assess the interference impact of an interfering base station in the network operating in accordance with a predefined time-frequency pattern, which specifies a first set of time-frequency resources at fixed first positions relative to a start of a specified frame, in which the interfering base station is to transmit first interfering signals at a first interfering power level and a second set of time-frequency resources at fixed second positions relative to the start of the specified frame, in which the interfering base station is to transmit second interfering signals at a second interfering power level, lower than the first interfering power level, while the wireless base station transmits downlink signals via the radio interface to user equipment, wherein the processor is also configured to instruct the user equipment, via the radio interface, to measure and report at least one parameter associated with reception of the downlink signals that is indicative of an effect of the interfering signals on the reception while the interfering transmitter operates in accordance with the predefined time-frequency pattern, and is configured to receive and process measurement results reported by the user equipment in order to assess the effect of the interfering signals.

18. The wireless base station according to claim 17 , operational to transmit, via the network interface or via the radio interface, the assessment of the effect of the interfering signals, to the base station the interfering transmitter belongs to or to a wireless network management entity.